British forces are on alert for an emergency deployment to Mali as David Cameron commits the UK to a fully-fledged battle against al-Qaeda in northern Africa.

The Times understands that units from the Army, Royal Navy and RAF are on “high readiness” to deploy if requested in support of France, which is attempting to repel Islamist extremists from the north of the country.

The paper says the "most striking" part of Cameron's speech was the fact he rejected the idea of "containing" the al-Qaeda threat and argued that the UK's ultimate aim was to "completely overcome them".

The move to put Britain's armed forces on alert for a possible deployment to Mali comes at a difficult time. The Army is preparing to make up to 5,000 soldiers redundant today in what is its third round of cost-cutting in recent times, despite already being stretched by Afghanistan campaign.